904 planetary question

What year is the planetary, and what year is the mainshaft.
Somewhere in the late 70s or early 80s, they changed the design of the splines, and even tho the parts physically inter-fit, the splines have a different shape, and when/if you are unlucky enough to find this out it will because the M/S machined out the hub, and Zing you are walking. For this reason I always consider the m/s and the planetaries as a set. When it happened to me,it was an aluminum planetary from an early trans swapped into a later box, with the later m/s. You know I looked at those splines for a very long time with a magnifying glass, and could not see the difference. I threw the m/s out and went and installed a matched set, and it never happened again.